My U.S. Pat. No. 3,885,258 discloses a multi-layer mattress which minimizes bodily irritations and supports the user's body in a level condition by providing maximum support in areas of greatest weight to prevent "hammocking" of the body. Such support is provided by an intermediate, relatively rigid support layer with a contoured surface having an inverted relationship to the relatively heavy areas of the human body.
My U.S. Pat. No. 4,053,957 provides a multi-layer mattress with another means of enhancing support of the relatively heavy areas of the body. Two transversely extending ribs of less compressibility than the material of the mattress's upper layer extend across a lower layer and are received in complementary recesses in the upper layer. Each support area in U.S. Pat. No. 4,053,957 is unitary and comprises one rib of a relatively large cross section.
Each of my prior patents provides uniform support in the user's shoulder area, buttocks area, etc. It has been found that it may be desirable to apply various degrees of localized support within the areas of enhanced support, since the force exerted by the body in these areas is not uniform, and to provide for shifting of body weight during sleep.